Enhanced accumulation of glycogen, lipids and polyhydroxybutyrate under optimal nutrients and light intensities in the cyanobacterium S ynechocystis sp. PCC 6803

Aims Glycogen ( GL ) and lipids ( LP ) are efficient biofuel substrates, whereas polyhydroxybutyrate ( PHB ) is a potent biodegradable plastic. This study aimed to increase accumulation of these three compounds in S ynechocystis sp. PCC 6803. Methods and Results Under autophototrophic growth, co‐accumulation of the three compounds reached maximum level in a mid‐stationary phase at 39·2% of dry weight (22·7% GL , 14·1% LP and 2·4% PHB ). Nitrogen deprivation increased this to 61·5% (36·8% GL , 11·2% LP and 13·5% PHB ), higher than that achieved by phosphorus, sulfur, iron or calcium deprivation. Combining nitrogen deprivation with 0·4% (w/v) glucose addition for heterophototrophic growth and optimizing the light intensity (200  μ mol photons m −2  s −1 ) synergistically enhanced combined accumulation to 71·1% of biomass (41·3% GL , 16·7% LP and 13·1% PHB ), a higher level than previously reported in Synechocystis . However, the maximum coproductivity of GL , LP and PHB (at 0·72 g l −1 ) was obtained in the 12‐day heterophototrophic culture without nitrogen deprivation. Conclusion Accumulation of GL , LP and PHB was enhanced under both autophototrophic and heterophototrophic conditions by optimizations of nutrient and light supplies. Significance and Impact of the Study This study provides a means for increasing co‐production of potent bioenergy substrates and useful biomaterials in S ynechocystis which may also be applicable to other cyanobacteria.